1. Field of the Invention
The present invention relates to an optical modulator module and a semiconductor optical modulator.
2. Description of the Related Art
Japanese Patent No. 4235154 and Japanese Unexamined Patent Application Publication No. 2010-008869 disclose InP-based modulators. K.-O. Velthaus, et. al, “High performance InP-based Mach-Zehnder modulators for 10 to 100 Gb/s optical fiber transmission systems,” 23rd International Conference on Indium Phosphide and Related Materials, IPRM 2011, Th-8.1.2 May 22-26, 2011, Berlin, Germany discloses another InP-based modulator.
The above-cited paper discloses an integrated optical device in which four Mach-Zehnder (MZ) modulators are integrated. A modulation signal for the push-pull modulation is applied to the individual waveguide arms through a single-phase transmission line having a characteristic impedance of 50 Ohm (Ω). The modulator is thus modulated by the modulation signal passing through the transmission line.
The modulator disclosed in Japanese Patent No. 4235154 is also modulated by applying a modulation signal to waveguide arms through a single-phase transmission line. Furthermore, in Japanese Unexamined Patent Application Publication No. 2010-008869, the MZ modulator is modulated by the modulation signal passing through a transmission line. Japanese Unexamined Patent Application Publication No. 2010-008869 discloses that the transmission line connected to the MZ modulator has a characteristic impedance of 50Ω.